Method and apparatus for reporting a channel quality in a wireless communication system

ABSTRACT

The present invention provided a method and apparatus for reporting a channel quality in a wireless communication system. A terminal receives an uplink grant from a base station via one of a plurality of downlink component carriers (CCs). The uplink grant includes a channel quality indicator (CQI) request for instructing uplink allocation and CQI reporting. The terminal reports the CQI of the downlink CC being linked to the base station. The downlink CC being linked is one of the plurality of downlink CCs, which is linked to the uplink CC for which the uplink allocation is scheduled. A method and an apparatus for reporting channel quality are discussed. The method according to an embodiment includes receiving, by a terminal configured with a plurality of downlink component carriers (CCs), control information from a base station, the control information including an uplink allocation and a CQI request, the control information including a carrier indicator field (CIF) indicating an uplink CC in which the uplink allocation is scheduled; and transmitting, by the terminal to the base station, the CQI through an uplink CC. The CQI request indicates one of: a triggering of CQI reporting for one downlink CC linked to the uplink CC, indicated by the CIF, among the plurality of downlink CCs; and a triggering of CQI reporting for a first group of downlink CCs among the plurality of downlink CCs.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Reissue application of U.S. Pat. No. 8,644,182issued on Feb. 4, 2014, which is the National Phase of PCT InternationalApplication No. PCT/KR2010/009002 filed on Dec. 16, 2010, which claimspriority the benefit under 35 U.S.C. §119(e) § 119(e) to U.S.Provisional Application No. 61/287,168 filed on Dec. 16, 2009, all ofwhich are hereby expressly incorporated by reference into the presentapplication. Notice: More than one reissue application has been filedfor the reissue of U.S. Pat. No. 8,644,182. The reissue applications areapplication Ser. Nos. 15/015,707 (the present application) and15/015,975 (continuation of the present application).

TECHNICAL FIELD

The present invention relates to wireless communications, and moreparticularly, to a method and apparatus for reporting channel quality ina wireless communication system.

BACKGROUND ART

In order to increase efficiency of a wireless communication system, itis essential to know channel quality. Quality of a downlink channel isreported by a base station to a user equipment. An indicator forindicating the channel quality is called a channel quality indicator(CQI) or a channel state indicator (CSI).

The CQI may be a value obtained by quantizing a channel state (e.g., asignal to interference-plus-noise ratio (SINR), a carrier tointerference and noise ratio (CINR), a bit error rate (BER), and a frameerror rate (FER)) or a modulation and coding scheme (MCS) index in anMCS table. In addition, the CQI may include a rank indicator (RI) and/ora precoding matrix indicator (PMI) in a multi-antenna system.

Long term evolution (LTE) based on 3^(rd) generation partnership project(3GPP) technical specification (TS) release 8 is a promisingnext-generation mobile communication standard.

In a typical wireless communication system, one component carrier isconsidered in general even if a bandwidth is differently set between anuplink and a downlink. In 3^(rd) 3GPP LTE, one carrier constitutes eachof the uplink and the downlink on the basis of a single carrier, and thebandwidth of the uplink is symmetrical to the bandwidth of the downlinkin general.

However, except for some areas of the world, it is difficult to allocatefrequencies of wide bandwidths. Therefore, as a technique foreffectively using fragmented small bands, a spectrum aggregationtechnique is being developed to obtain the same effect as when a band ofa logically wide bandwidth is used by physically aggregating a pluralityof bands in a frequency domain.

The spectrum aggregation includes a technique for supporting a systembandwidth of 100 mega Hertz (MHz) by using multiple carriers even if,for example, the 3GPP LIE supports a bandwidth of up to 20 MHz, and atechnique for allocating an asymmetric bandwidth between the uplink andthe downlink.

The 3GPP LTE is designed to report channel quality on the basis of asingle-component carrier. However, with the introduction of multiplecarriers, there is a need for a method capable of reporting channelquality in a multi-carrier system.

SUMMARY OF INVENTION Technical Problem

The present invention provides a method and apparatus for reportingchannel quality in a wireless communication system.

Technical Solution

In an aspect, a method for reporting channel quality in a wirelesscommunication system includes receiving an uplink grant from a basestation through one of a plurality of downlink component carriers (CCs),the uplink grant including an uplink allocation and a channel qualityindicator (CQI) indicating a triggering of CQI reporting, and reportinga CQI of a linked downlink CC to the base station. The linked downlinkCC is a downlink CC linked to an uplink CC in which the uplinkallocation is scheduled among the plurality of downlink CCs.

The uplink grant may further include a carrier indicator field (CIF)indicating the uplink CC in which the uplink allocation is scheduled.

The method may further include receiving system information including afirst CC linkage between at least one uplink CC and the plurality ofdownlink CCs from the base station. The uplink CC in which the uplinkallocation is scheduled may be determined according to the first CClinkage.

The method may further include receiving a radio resource control (RRC)message including a second CC linkage between at least one uplink CC andthe plurality of downlink CCs from the base station. The uplink CC inwhich the uplink allocation is scheduled may be determined according tothe second CC linkage.

In another aspect, an apparatus configured for reporting channel qualityin a wireless communication system is provided. The apparatus includes aradio frequency (RF) unit configured for transmitting and receiving aradio signal, and a processor coupled to the RF unit and configured forreceiving an uplink grant from a base station through one of a pluralityof downlink component carriers (CCs), the uplink grant including anuplink allocation and a channel quality indicator (CQI) indicating atriggering of CQI reporting, and reporting a CQI of a linked downlink CCto the base station. The linked downlink CC is a downlink CC linked toan uplink Cc in which the uplink allocation is scheduled among theplurality of downlink CCs.

Advantageous Effects

The present invention provides a method for transmitting a controlsignal in a multi-carrier system capable of cross carrier scheduling.More specifically, a method and apparatus for reporting channel qualityare proposed.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a downlink radio frame structure in 3^(rd) generationpartnership project (3GPP) long term evolution (LTE).

FIG. 2 shows channel quality indicator (CQI) reporting in theconventional 3GPP LTE.

FIG. 3 shows an example of multiple carriers

FIG. 4 shows an example of a multi-carrier operation.

FIG. 5 shows an example of cross-carrier scheduling.

FIG. 6 is a diagram for describing an operation according to anembodiment of the present invention.

FIG. 7 is a flowchart showing a CQI reporting method according to anembodiment of the present invention.

FIG. 8 is a block diagram showing a wireless communication systemaccording to an embodiment of the present invention.

MODE FOR INVENTION

A user equipment (UE) may be fixed or mobile, and may be referred to asanother terminology, such as a mobile station (MS), a mobile terminal(MT), a user terminal (UT), a subscriber station (SS), a wirelessdevice, a personal digital assistant (PDA), a wireless modem, a handhelddevice, etc.

A base station (BS) is generally a fixed station that communicates withthe UE and may be referred to as another terminology, such as an evolvednode-B (eNB), a base transceiver system (BTS), an access point, etc.

Each BS provides a communication service to a specific geographicalregion (generally referred to as a cell). The cell can be divided into aplurality of regions (referred to as sectors).

FIG. 1 shows a downlink radio frame structure in 3^(rd) generationpartnership project (3GPP) long term evolution (LTE). The section 6 of3GPP TS 36.211 V8.7.0 (2009-05) “Evolved Universal Terrestrial RadioAccess (E-UTRA); Physical Channels and Modulation (Release 8)” may beincorporated herein by reference.

A radio frame consists of 20 subframes indexed with 0 to 19. Onesubframe consists of 2 slots. A time required for transmitting onesubframe is defined as a transmission time interval (TTI). For example,one subframe may have a length of 1 millisecond (ms), and one slot mayhave a length of 0.5 ms.

One slot may include a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols in a time domain. Since the 3GPP LTE usesorthogonal frequency division multiple access (OFDMA) in a downlink(DL), the OFDM symbol is only for expressing one symbol period in thetime domain, and there is no limitation in a multiple access scheme orterminologies. For example, the OFDM symbol may also be referred to asanother terminology such as a single carrier frequency division multipleaccess (SC-FDMA) symbol, a symbol period, etc.

Although it is described that one slot includes 7 OFDM symbols forexample, the number of OFDM symbols included in one slot may varydepending on a length of a cyclic prefix (CP). According to 3GPP TS36.211 V8.7.0, in case of a normal CP, one subframe includes 7 OFDMsymbols, and in case of an extended CP, one subframe includes 6 OFDMsymbols.

A resource block (RB) is a resource allocation unit, and includes aplurality of subcarriers in one slot. For example, if one slot includes7 OFDM symbols in a time domain and the RB includes 12 subcarriers in afrequency domain, one RB can include 7×12 resource elements (REs).

A DL subframe is divided into a control region and a data region in thetime domain. The control region includes up to three preceding OFDMsymbols of a 1^(st) slot in the subframe. The number of OFDM symbolsincluded in the control region may vary. A physical downlink controlchannel (PDCCH) is allocated to the control region, and a physicaldownlink shared channel (PDSCH) is allocated to the data region.

As disclosed in 3GPP TS 36.211 V8.7.0, the 3GPP LTE classifies aphysical channel into a data channel and a control channel. Examples ofthe data channel include a physical downlink shared channel (PDSCH) anda physical uplink shared channel (PUSCH). Examples of the controlchannel include a physical downlink control channel (PDCCH), a physicalcontrol format indicator channel (PCFICH), a physical hybrid-ARQindicator channel (PHICH), and a physical uplink control channel(PUCCH).

The PCFICH transmitted in a 1^(st) OFDM symbol of the subframe carries acontrol format indicator (CFI) regarding the number of OFDM symbols(i.e., a size of the control region) used for transmission of controlchannels in the subframe. The UE first receives the CFI through thePCFICH, and thereafter monitors the PDCCH.

The PHICH carries a positive-acknowledgement(ACK)/negative-acknowledgement (HACK) signal for uplink hybrid automaticrepeat request (HARQ). The ACK/NACK signal for uplink (UL) data on thePUSCH transmitted by the UE is transmitted on the PHICH.

Control information transmitted through the PDCCH is referred to asdownlink control information (DCI). The DCI may include a resourceallocation of the PDSCH (this is referred to as a DL grant), a resourceallocation of a PUSCH (this is referred to as a UL grant), a set oftransmit power control commands for individual UEs in any UE groupand/or activation of a voice over Internet protocol (VoIP).

The DCI on the PDCCH is received by using blind decoding. A plurality ofcandidate PDCCHs can be transmitted in the control region of onesubframe. The UE monitors the plurality of candidate PDCCHs in everysubframe. Herein, monitoring is an operation in which the UE attemptsdecoding of each PDCCH according to a format of PDCCH to be monitored.The UE monitors a set of PDCCH candidates in a subframe to find its ownPDCCH. For example, if there is no cyclic redundancy check (CRC) errordetected by performing de-making on an identifier (i.e., cell-radionetwork temporary identifier (RNTI)) of the UE in a corresponding PDCCH,the UE detects this PDCCH as a PDCCH having its DCI.

In order to receive DL data, the UE first receives a DL grant on thePDCCH. DL data on the PDSCH is received by using the DL grant. Inaddition, to transmit UL data, the UE first receives a UL grant on thePDCCH. UL data is transmitted on the PUSCH by using the UL grant.

A physical broadcast channel (PBCH) is transmitted in first four OFDMsymbols in a 2^(nd) slot of a 1^(st) subframe of a radio frame. The PBCHcarries system information necessary for communication between a UE anda BS. The system information transmitted through the PBCH is referred toas a master information block (MIB). In comparison thereto, systeminformation transmitted through the PDCCH is referred to as a systeminformation block (SIB).

Now, channel quality reporting in 3GPP LTE will be described withreference to the section 7.2 of 3GPP TS 36.213 V8.7.0(2009-05).

FIG. 2 shows CQI reporting in the conventional 3GPP LTE.

ABS transmits a CQI request 201 through a PDCCH in a DL subframe. TheCQI request 201 is included in a DCI format 0 or a random accessresponse. The DCI format 0 is used for transmission of a UL grant. TheUL grant further includes a UL resource allocation for a PUSCH.

The CQI request 201 indicates whether CQI reporting is triggered byusing a 1-bit field. For example, if a value of the CQI request 201 isset to ‘1’, it means that the BS requests the UE to perform CQIreporting.

If the CQI request 201 indicates the triggering of the CQI reporting,the UE transmits a CQI 202 to the BS through a PUSCH.

Since the UE reports the CQI at the request of the BS, this is calledaperiodic CQI reporting.

In 3GPP LTE, there are three types of CQI feedback, that is, Wideband,UE selected, and Higher layer-configured. In addition, there are alsothree types of PMI feedback, that is, No PMI, Single PMI, and MultiplePMI. According to the CQI feedback type and the PMI feedback type, atransmission mode is divided as shown in Table 1 below.

TABLE 1 No PMI Single PMI Multiple PMI Wideband Mode 1-2 (wideband CQI)UE selected Mode 2-0 Mode 2-2 (subband CQI) Higher layer- Mode 3-0 Mode3-1 configured (subband CQI)

According to the mode 1-2, a PMI is selected under the assumption thatdata is transmitted in each subband. The UE determines a CQI by assumingthe selected PMI with respect to a system band or a whole banddesignated by a higher layer (such a band is called a set S). The UEtransmits the CQI and the PMI of each subband. Since the CQI of a wholeband or subbands included in the set S is transmitted, it is called awideband CQI. A size of each subband may vary depending on a size of thesystem band.

According to the mode 2-0, the UE selects M (M>0) preferred subbands inthe system band or the set S. The UE determines a CQI for the selected Msubbands (such a subband is called a subband CQI). In addition, the UEadditionally determines a wideband CQI with respect to the system bandor the set S. The UE transmits the selected M subbands, one CQI for theselected M subbands, and the wideband CQI.

According to the mode 2-2, M preferred subbands and a single PMI for theM preferred subbands are determined. In addition, the UE determines awideband CQI with respect to the system band or the set S. The UEtransmits the selected M subbands, one CQI for the selected M subbands,a single PMI for the M selected subbands, and a wideband CQI.

According to the mode 3-0, the UE determines the wideband CQI. Further,the UE determines a CQI for each subband.

According to the mode 3-1, the UE determines a single PMI with respectto the system band or the set S. The UE determines a wideband CQI and asubband CQI for each subband by assuming the single PMI.

Meanwhile, uplink power control is used in the wireless communicationsystem. The BS increases uplink power when a channel environment is notgood, and decreases the uplink transmit power when the channelenvironment is good. This is to decrease interference to a neighboringcell due to excessive transmit power and to optimize a power usageamount as much as possible.

In 3GPP LTE, a transmit power command (TPC) is used for uplink transmitpower control, and transmit power is controlled independently in each ofa PUCCH and a PUSCH. In general, the TPC for the PUCCH used intransmission of an HARQ ACK/NACK signal is included in a DL grant.Further, the TPC for the PUSCH is included in a UL grant.

Now, a multiple-carrier system will be described.

To support a higher data rate, a multiple-carrier system supporting aplurality of component carriers (CCs) is taken into account.

Spectrum aggregation (or bandwidth aggregation, also referred to ascarrier aggregation) supports a plurality of CCs. The spectrumaggregation is introduced to support an increasing throughput, toprevent a cost increase caused by using a broadband radio frequency (RF)element, and to ensure compatibility with legacy systems. For example,if 5 CCs are assigned as a granularity of a carrier unit having abandwidth of 20 MHz, a bandwidth of up to 100 MHz can be supported.

FIG. 3 shows an example of multiple carriers. Although three DL CCs andthree UL CCs are shown herein, the number of DL CCs and the number of ULCCs are not limited thereto. A PDCCH and a PDSCH are independentlytransmitted in each DL CC. A PUCCH and a PUSCH are independentlytransmitted in each UL CC.

FIG. 4 shows an example of a multi-carrier operation. Even if amulti-carrier system supports a plurality of CCs, the number ofsupported CCs may differ depending on a cell or UE capability.

An available CC indicates all CCs that can be used by the system.Herein, there are 6 CCs (i.e., CC #0 to CC #5).

An assigned CC is a CC assigned by a BS to a UE according to the UEcapacity among available CCs. Although it is shown that the CC #0 to theCC #3 are assigned CCs, the number of assigned CCs may be less than orequal to the number of available CCs.

An active CC is a CC used by the UE to perform reception and/ortransmission of a control signal and/or data with respect to the BS. TheUE can perform PDCCH monitoring and/or PDSCH buffering with respect tosome or all of the active CCs. The active CCs can be activated ordeactivated among the assigned CCs. Among the active CCs, a CC which isalways activated is called a reference CC.

In a multi-carrier system, a CC linkage can be defined between a DL CCand a UL CC. The CC linkage implies a mapping relation between a DL CCin which a PDCCH for carrying a UL grant is transmitted and a UL CCscheduled by the UL grant. Alternatively, the CC linkage may be amapping relation between a DL CC (or UL CC) in which data for HARQ istransmitted or a UL CC (or DL CC) in which an HARQ ACK/NACK signal istransmitted. The CC linkage may be a relationship between a DL CC whichis a target of CQI reporting and a UL CC for transmitting a CQI.

The example of FIG. 3 shows a symmetric CC linkage in which a DL CC anda UL CC are one-to-one mapped.

The CC linkage can be configured as a static CC linkage and a dynamic CClinkage as follows.

In a first method, the CC linkage is fixed. This is called a fixed CClinkage or a static CC linkage. This can be signaled by using systeminformation which is common information. Since a UL CC to be scheduledby a UL grant can be determined through the static CC linkage,additional signaling for configuring a linkage between a UL CC and a DLCC and transmitted for each UE is not necessary.

In a second method, the CC linkage is dynamically or semi-staticallychanged or overridden. This is called the dynamic CC linkage. This canbe reported by the BS to the UE by using a radio resource control (RRC)message or L1/L2 signaling. The dynamic CC linkage can be UE-specific(in this case, it can be specific for each CC or may be common for eachCC), or can be UE group-specific or cell-specific. The dynamic CClinkage can be mapped in a 1:1 manner or 1:M or M:1 manner

Two methods are possible as CC scheduling.

In a first method, a fixed CC linkage is utilized. A UL grant istransmitted through a DL CC. A UL transport block is transmitted byusing the UL grant through a UL CC linked to the DL CC. Since a UL CC tobe scheduled by the UL grant can be determined through a predefined CClinkage, additional signaling is not necessary.

In a second method, a CC to be scheduled is directly indicated. Forexample, a PDCCH and a PDSCH are transmitted in different DL CCs, or aPUSCH is transmitted through a UL CC not linked to a DL CC in which thePDCCH is transmitted. This is called cross-carrier scheduling.

FIG. 5 shows an example of cross-carrier scheduling. It is assumed thata DL CC #0 is linked to a UL CC #0, a DL CC #1 is linked to a UL CC #1,and a DL CC #2 is linked to a UL CC #2.

A 1^(st) PDCCH 710 701 of the DL CC #0 carries DCI for a PDSCH 702 ofthe same DL CC #0. A 2^(nd) PDCCH 711 of the DL CC #0 carries DCI for aPDSCH 712 of the DL CC #1. A 3^(rd) PDCCH 721 of the DL CC #0 carriesDCI for a PUSCH 722 723 of the unlinked UL CC #2.

For cross-carrier scheduling, the DCI of the PDCCH may include a carrierindicator field (CIF). The CIF indicates a DL CC or a UL CC scheduledthrough the DCI. The CIF may include an index of a UL CC or an index ofa DL CC scheduled through the DCI. For example, the 2^(nd) PDCCH 711 mayinclude a CIF indicating the DL CC #1. The 3^(rd) PDCCH 721 may includea CIF indicating the UL CC #2.

As described above, in the conventional 3GPP LTE, a UL frequency bandand a DL frequency band correspond to each other, and only one UL andone DL CC are present. Therefore, a TPC included in DCI for a DL grantis control information for a UL CC corresponding to a DL CC, and a CQIrequest included in DCI for a UL grant is control information for a DLCC corresponding to a scheduled UL CC.

However, an ambiguity may occur in a multi-carrier system using aplurality of CCs according to the conventional 3GPP LTE structure.

More specifically, a 3^(rd) PDCCH 721 transmitted through a DL CC #0carries a UL grant for scheduling a UL CC #2. Assume that the UL CC #2is linked to a DL CC #2. In this case, when a CQI request is included inthe UL grant, whether the CQI request is a CQI for one DL CC or a CQIfor a DL CC group (or all CCs)or which CC(s) is a target DL CC thereofmay be ambiguous.

For example, if the CQI request is for one CC, it may be ambiguouswhether the CQI request is for requesting CQI reporting for the DL CC #0in which the 3^(rd) PDCCH 721 is transmitted or is for requesting CQIreporting for the DL CC #2 linked to the UL CC #2 in which the UL grantis scheduled.

FIG. 6 is a diagram for describing an operation according to anembodiment of the present invention. Although there are 5 DL CCs and 5UL CCs, the number of CCs is not limited thereto. It is assumed that aDL CC #k (0<=k<=4) is linked to a UL CC #k according to a static CClinkage. The static CC linkage can be reported by the BS to the UE byusing a part of system information (i.e., MIB or SIB).

It is assumed that a CIF consists of 3 bits, and each value is definedby Table 2 below.

TABLE 2 CIF value Description 0 UL CC index 0 1 UL CC index 1 2 UL CCindex 2 3 UL CC index 3 4 UL CC index 4 5 Reserved 6 Reserved 7 UL CCindex 0, dynamic CC linkage

Hereinafter, a CC index of a CIF in a UL grant is an index of a UL CCscheduled by the UL grant. However, in another example, a CC index of aCIF in a UL grant may be an index of a DL CC linked to a UL CC to bescheduled by the UL grant.

DCI of a 1^(st) PDCCH 801 of the DL CC #1 includes a UL grant forscheduling the UL CC #0. The UL grant includes a UL resource allocation802, a CQI request, and a CIF.

If a value of the CQI request is 0, CQI reporting is not triggered, andif the value of the CQI request is 1, CQI reporting is triggered.

Assume that the value of the CIF included in the UL grant of the 1^(st)PDCCH 801 is set to 0, i.e., an index of the UL CC #0. When CQIreporting is triggered, the UE can report a CQI for the DL CC #0 linkedto a UL CC having a CC index 0 (i.e., UL CC #0). That is, when CQIreporting is triggered, the UE reports a CQI of a DL CC linked to a ULCC indicated by a CIF included in the UL grant.

Assume that CQI reporting is triggered, and the CIF value is set to 7which indicates the dynamic CC linkage. When the CIF value is 7, a UL CCin which a UL grant is scheduled can be predetermined. In this example,if the CIF value is 7, it indicates the UL CC #0. The CIF valueindicating the dynamic CC linkage is for exemplary purposes only, andthus can be set to any specific value. When the CIF value indicates thedynamic CC linkage, a UL CC scheduled by a UL grant may be a UL CCdefined by a higher layer message such as an RRC message, or may be a ULCC which is predetermined to transmit a control signal.

The dynamic CC linkage indicates CC mapping for CQI reporting. Thedynamic CC linkage can indicate at least any one of the following fourtypes.

(1) all available DL CCs

(2) all active DL CCs

(3) all assigned DL CCs

(4) a DL CC group (or DL CC list) including at least one DL CC

That is, if the dynamic CC linkage type (4) is used, the UE reports aCQI for DL CCs in a DL CC group.

The dynamic CC linkage may be pre-defined, or may be transmitted by theBS to the UE by using a radio resource control (RRC) message or L1/L2signaling. The dynamic CC linkage may be UE-specific, UE group-specific,or cell-specific. The dynamic linkage may be specific for each CC orcommon for each CC.

Which type of dynamic CC linkage will be used can be reported by the BSto the UE by using the RRC message. If the dynamic CC linkage type (4)is used, information regarding a DL CC group for reporting a CQI can bereported by the BS to the UE by using the RRC message.

One or more dynamic CC linkages can be used. In the example of Table 2,if the CIF value is 6, it may indicate the dynamic CC linkage type (1),and if the CIF value is 7, it may indicate the dynamic CC linkage type(4). Alternatively, it is also possible to designate a plurality ofdynamic CC linkage types (4) each of which can be designated by using aCIF. For example, if the CIF value is 6, it indicates DL CCs #0 and #1,and if the CIF value is 7, it indicates the DL CCs #2 to #4.

DCI of a 2^(nd) PDCCH 811 of a DL CC #2 includes a DL grant for a DL CC#3. The DL grant includes a DL resource allocation 812, a CIF, and aTPC. Assume that the CIF value is set to 3 which is an index of the DLCC #3. The TPC may be a TPC for a UL CC #3 linked to the DL CC #3.Alternatively, the TPC may be a TPC for the UL CC #2 linked to the DL CC#2 in which the 2^(nd) PDCCH 811 is transmitted.

Although it is shown in this example that the TPC is included in the DLgrant, the TPC may be included in a UL grant. In this case, the TPC maybe a TPC for a UL CC indicated by the CIF. Alternatively, the TPC may bea TPC for a UL CC linked to a DL CC in which the UL grant istransmitted.

The proposed invention is also applicable to not only CQI reportingand/or TPC transmission but also other control signals. A CQI request isa signal used when the BS requests the UE to set or trigger a controlsignal for a corresponding DL CC (or UL CC), and can be called a controlsetup signal or a control trigger signal.

The dynamic CC linkage is not determined by a specific CIF value, butcan be predetermined by using an RRC message or the like. If the CQIrequest is 0, the UE may not transmit the CQI report, and if the CQIrequest is 1, the UE may transmit the CQI report according to a dynamicCC linkage determined by using the RRC message.

Although a case where the CQI request is 1 bit is considered in theaforementioned example, more various examples may be possible if thenumber of bits of the CQI request is increased. Table 3 below shows aconfiguration depending on each value when the CQI request is 2 bits.

TABLE 3 Value of CQI request Description 0 No CQI reporting 1 CQIreporting based on static CC linkage 2 CQI reporting based on 1^(st)dynamic CC linkage 3 CQI reporting based on 2^(nd) dynamic CC linkage

If the CQI request value is 1, the UE reports the CQI according to thestatic CC linkage. For example, upon receiving a UL grant for a UL CC#1, the UE reports a CQI for a DL CC linked to the UL CC #1. If the CQIrequest value is 2 or 3, the UE reports a CQI according to thepre-defined 1^(st) or 2^(nd) dynamic CC linkage. The 1^(st) and 2^(nd)dynamic CC linkages can be determined by using an RRC message.

Now, an example of CQI reporting will be described in greater detail.

FIG. 7 is a flowchart showing a CQI reporting method according to anembodiment of the present invention.

A UE receives a 1^(st) CC linkage from a BS (step S910). The 1^(st) CClinkage can be received as a part of system information, and can becalled a static CC linkage.

The UE receives a 2^(nd) CC linkage from the BS (step S920). The 2^(nd)CC linkage can be received by using an RRC message, and can be called adynamic CC linkage.

The UE receives a UL grant including a CQI request from the BS (stepS930). For example, the CQI request can be configured as shown in Table3.

When the CQI request is triggered, the UE determines a DL CC in which aCQI is reported according to the CQI request (step S940). For example,if the CQI request value is 3, the UE can determine a DL CC linked basedon the 2^(nd) CC linkage, that is, the dynamic CC linkage.Alternatively, if the CQI request value is 2, the UE can determine a DLCC linked based on the 1^(st) CC linkage, that is, the static CClinkage. Determining of the DL CC according to the dynamic CC linkageand the static CC linkage is described in the embodiment of FIG. 6.

The UE reports a CQI for the determined DL CC to the BS (step S950).

FIG. 8 is a block diagram showing a wireless communication systemaccording to an embodiment of the present invention.

A BS 50 includes a processor 51, a memory 52, and a radio frequency (RF)unit 53. The memory 52 is coupled to the processor 51, and stores avariety of information for driving the processor 51. The RF unit 53 iscoupled to the processor 51, and transmits and/or receives a radiosignal. The processor 51 implements the proposed functions, procedures,and/or methods. The processor 51 can implement an operation of the BS 50according to the embodiments of FIG. 6 and FIG. 7.

A UE 60 includes a processor 61, a memory 62, and an RF unit 63. Thememory 62 is coupled to the processor 61, and stores a variety ofinformation for driving the processor 61. The RF unit 63 is coupled tothe processor 61, and transmits and/or receives a radio signal. Theprocessor 61 implements the proposed functions, procedures, and/ormethods. The processor 51 can implement an operation of the UE 60according to the embodiments of FIG. 6 and FIG. 7.

The processor may include Application-Specific Integrated Circuits(ASICs), other chipsets, logic circuits, and/or data processors. Thememory may include Read-Only Memory (ROM), Random Access Memory (RAM),flash memory, memory cards, storage media and/or other storage devices.The RF unit may include a baseband circuit for processing a radiosignal. When the above-described embodiment is implemented in software,the above-described scheme may be implemented using a module (process orfunction) which performs the above function. The module may be stored inthe memory and executed by the processor. The memory may be disposed tothe processor internally or externally and connected to the processorusing a variety of well-known means.

In the above exemplary systems, although the methods have been describedon the basis of the flowcharts using a series of the steps or blocks,the present invention is not limited to the sequence of the steps, andsome of the steps may be performed at different sequences from theremaining steps or may be performed simultaneously with the remainingsteps. Furthermore, those skilled in the art will understand that thesteps shown in the flowcharts are not exclusive and may include othersteps or one or more steps of the flowcharts may be deleted withoutaffecting the scope of the present invention.

The above-described embodiments include various aspects of examples.Although all possible combinations for describing the various aspectsmay not be described, those skilled in the art may appreciate that othercombinations are possible. Accordingly, the present invention should beconstrued to include all other replacements, modifications, and changeswhich fall within the scope of the claims.

The invention claimed is:
 1. A method for reporting channel quality by adevice in a wireless communication system, the method comprising:receiving, by the device, an uplink grant on control information via aphysical downlink control channel (PDCCH) through one of a plurality ofdownlink component carriers (CCs), the uplink grant the controlinformation including an uplink allocation and, a channel qualityindicator (CQI) request indicating a triggering of CQI reporting and acarrier indicator (CI) indicating an uplink CC in which the uplinkallocation is scheduled, wherein, when a value of related to the CQIrequest is set to a first value, the CQI request indicates thetriggering of CQI reporting is a CQI reporting is triggered for the onedownlink CC of the plurality of downlink CCs linked to the uplink CC,which is linked to the uplink CC indicated by the CI, wherein when thevalue of related to the CQI request is set to a second value, the CQIrequest indicates the triggering of CQI reporting is the CQI reportingis triggered for a first set of downlink CCs of the plurality ofdownlink CCs, and wherein when the value ofrelated to the CQI request isset to a third value, the CQI request indicates the triggering of CQIreporting isthe CQI reporting is triggered for a second set of downlinkCCs of the plurality of downlink CCs; and reporting, by the device, aCQI for a downlink CC indicated by the CQI request through an via aphysical uplink shared channel (PUSCH) of the uplink CC based on the CQIrequest and the uplink allocation of the PDCCH.
 2. The method of claim1, wherein the uplink grant further includes a carrier indicator field(CIF) indicating the uplink CC in which the uplink allocation isscheduled.
 3. The method of claim 1, wherein a number of bits for theCQI request is two.
 4. The method of claim 1, further comprising:receiving information on the first set of downlink CCs and the secondset of downlink CCs.
 5. The method of claim 1, wherein a linkage betweenthe one of the plurality of downlink CCs linked to downlink CC and theuplink CC is received via system information.
 6. The method of claim 1,wherein the first value is “1,” the second value is “2,” and the thirdvalue is “3.”
 7. An apparatus configured for reporting channel qualityin a wireless communication system, the apparatus comprising: a radiofrequency (RF) unit configured to transmit and receive a radio signal;and a processor coupled to the RF unit and configured to: receive anuplink grant on control information via a physical downlink controlchannel (PDCCH) through one of a plurality of downlink componentcarriers (CCs), the uplink grant control information including an uplinkallocation and, a channel quality indicator (CQI) request indicating atriggering of CQI reporting; and a carrier indicator (CI) indicating anuplink CC in which the uplink allocation is scheduled, wherein, when avalue of related to the CQI request is set to a first value, the CQIrequest indicates the triggering of CQI reporting is a CQI reporting istriggered for the one downlink CC of the plurality of downlink CCslinked to the uplink CC, which is linked to the uplink CC indicated bythe CI, wherein when the value of related to the CQI request is set to asecond value, the CQI request indicates the triggering of CQI reportingis reporting is triggered for a first set of downlink CCs of theplurality of downlink CCs, and wherein when the value ofrelated to theCQI request is set to a third value, the CQI request indicates thetriggering of CQI reporting isreporting is triggered for a second set ofdownlink CCs of the plurality of downlink CCs;, and report a CQI for adownlink CC indicated by the CQI request through an via a physicaluplink shared channel (PUSCH) of the uplink CC based on the CQI requestand the uplink allocation of the PDCCH.
 8. The apparatus of claim 7,wherein the uplink grant further includes a carrier indicator field(CIF) indicating the uplink CC in which the uplink allocation isscheduled.
 9. The apparatus of claim 7, wherein a number of bits for theCQI request is two.
 10. The apparatus of claim 7, wherein the processoris configured to receive information on the first set of downlink CCsand the second set of downlink CCs.
 11. The apparatus of claim 7,wherein a linkage between the one of the plurality of downlink CCslinked to the uplink CC is received via system information.
 12. Theapparatus of claim 7, wherein the first value is “1,” the second valueis “2,” and the third value is “3.”
 13. The method of claim 1, whereinthe CQI reporting based on the CQI request corresponds to an aperiodicCQI.
 14. The method of claim 1, wherein when the value related to theCQI request is set to the first value, the one downlink CC is identifiedby a linkage with the uplink CC indicated by the CI.